SOLUTION: Vinnie drives his car 175 miles and has an average of a certain speed. If the average speed had been 4mph more, he could have traveled 189 miles in the same length of time. What wa

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Question 1157811: Vinnie drives his car 175 miles and has an average of a certain speed. If the average speed had been 4mph more, he could have traveled 189 miles in the same length of time. What was his average speed?

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
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175 miles and has an average of a certain speed. If the average speed had been 4mph more, he could have traveled 189 miles in the same length of time.
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                    SPEED       TIME      DISTANCE

TRAVELED             r           x         175

NEW CONDITION      r+4           x         189


ALL IN VARIABLES
TRAVELED            r           x         D
NEW COND          r+k           x         N

D%2Fr=N%2F%28r%2Bk%29
-
r%2FD=%28r%2Bk%29%2FN
rN=D%28r%2Bk%29
Nr=Dr%2BDk
Nr-Dr=Dk
r%28N-D%29=Dk
highlight%28r=Dk%2F%28N-D%29%29
Substitute your given values.

Answer by ikleyn(52854) About Me  (Show Source):
You can put this solution on YOUR website!
.

Let x be his average speed.

Then the other speed is (x+4) mph.


From the condition, you have this equation


    175%2Fx = 189%2F%28x%2B4%29.


Cross multiply, simplify and solve for x


    175*(x+4) = 189x

    175x + 4*175 = 189x

    4*175 = 189x - 175x

    4*175 = 14x

    x     = %284%2A175%29%2F14 = 50.


ANSWER. The average speed was 50 miles per hour.

Solved.